In Curran, et al. U.S. Pat. No. 4,173,314, an apparatus is disclosed for continuously supplying web material to a web printer. The web material is fed from a first roll that is supported in a feed position and, when the first roll is near depletion, the leading end of a second roll is adhesively connected to the web of the first roll with that web then being severed. A pair of parallel belts are employed for rotating both the forward and rearward rolls in order for both rolls to achieve the same speed for the connecting and severing operations. We have found that this prior art system does not work properly because the surface speeds of the first and second rolls are not the same when the rolls are of a different diameter. In addition, the paper from a roll tends to telescope when the roll diameter is relatively small and the wrap is not tight. If the belts apply a high pressure against the loose wrap, the chance of telescoping is even greater. If the belt tension is reduced in order to alleviate the telescoping problem, there may be slippage of the belts. There may also be a tracking problem because the belts are so long in that they are used to drive both of the rolls, and one of the belts may jump the pulleys.
Thus the prior art web supply apparatus discussed above has several disadvantages including problems in maintaining tension on the very long belts required, problems with belt tracking, tension upsets caused by the relative motion between the belts and the center line of the roll, and speed mismatches caused by differences in the distances that the belts contact the rolls or "wrap" which prevent an exact speed match between the expiring roll and the new roll.
It is desirable to have a system in which a continuous supply of web material may be supplied, with the disadvantages discussed above being alleviated. We have discovered an apparatus for supplying a continuous, uninterrupted web of material that does not require one or more belts for rotating both the forward and rearward rolls and thus does not have the problems described above.
Another problem that is found on high speed automatic machines, and web presses in particular, is the inherent delay between the time of a signal for a mechanism to activate and the time that the mechanism's function is completed. For example, the delay between the time that a signal is given for the knife to cut the expired web after it has been attached to the web from the new roll and the time that the cutting is actually completed may cause certain problems. In a high speed automatic splicer, it is necessary that the residual paper that remains attached to the new roll after the splice from the expired roll be kept as short as possible in order to reduce the probability of jamming the folder. The length of the glued area is approximately 15 inches and the overall length from the beginning of the paste to where the expired web was severed should be no more than 20 inches. Unfortunately, the delay time in the operation of the knife is typically equivalent to over two feet of paper. It is, therefore, necessary that the signal for the knife to cut the expired web be given at a time such that, irrespective of the delay in the knife firing, the cut will occur at the proper place. This anticipation of the signal time must be proportional to the speed of the machine with the anticipation being near zero at extremely low speeds and the full amount of the delay at high speeds. Previously, means to accomplish this anticipation have resulted in complex electronic devices using analog principles which have an inherent tendency to vary with temperatures, time, supply voltage, etc.
We have invented a system using timing means which are extremely accurate at any speed likely to be encountered on a printing press. Our invention anticipates the signal time but does not require complex electronic devices as required by prior art systems.